In various image pickup apparatuses such as a video camera and a still camera, an optical system including a lens group, an optical device, and the like therein and an image pickup device that photoelectrically converts light taken in by the optical system are arranged. In such an image pickup apparatus, there is a type in which light enters an image pickup device via a shutter apparatus or the like that functions as a blade opening/closing apparatus at a time a subject is photographed.
As the blade opening/closing apparatus, there is a type that includes a base body having an aperture formed therein, an opening/closing blade that is moved with respect to the base body, and a driving body that causes the opening/closing blade to move, and the driving body is operated by a driving force of a drive source, so that the opening/closing blade is moved so as to open/close the aperture between an opening position and a closing position.
In such a blade opening/closing apparatus, there is a type that includes a braking mechanism to control a movement speed of the opening/closing blade (see, for example, Patent Literature 1 and Patent Literature 2).
The blade opening/closing apparatus described in Patent Literature 1 is configured such that a rotatable coupling ring that functions as a driving body includes a projection, the projection comes into contact with a bias spring, a bias force having a magnitude corresponding to a rotation position of the coupling ring is applied from the bias spring, and a rotation speed of the coupling ring is lowered.
The blade opening/closing apparatus described in Patent Literature 2 is configured such that a rotatable sector ring that functions as a driving body includes a brake pin and a bifurcated brake lever for which a magnitude of a turning force is controlled by a spring washer, and when the driving body is rotated, the brake pin comes into contact with the brake lever and the rotation speed of the sector ring is lowered.
In such a manner, the blade opening/closing apparatuses described in Patent Literature 1 and Patent Literature 2 each include a braking mechanism that lowers the rotation speed of the driving body, and immediately before the opening/closing blade reaches the closing position from the opening position and immediately before the opening/closing blade reaches the opening position from the closing position, a braking force is applied to the opening/closing blade via the driving body. By application of the braking force to the opening/closing blade, a bound by a reaction caused after the opening/closing blade is moved to the closing position or the opening position less easily occurs, and the opening/closing blade can be stably held at the closing position and the opening position.